Oh, I thought activation and moving/freezing were the same thing. Is activation more like a hostile mob going aggro?

The slimes don't move at all when I'm beyond a certain distance. They spawn in and don't move, or they stop moving (freeze.) The distance isn't always the same. They aren't despawning. They just stop jumping even though I'm about a chunk and a half away.

I think activation range would be how far from you something will spawn. In a normal SP game mobs would spawn 128 away from you without freezing. On EMC it's 32 to help with lagging, etc. This is why some farms need to use a method to move the mobs to where they need them when they spawn outside of the 32 block range.

16 is where they get aggressive, thats why its at 18, and even if it was lower, all it would do is make it take up to 1 second longer before they attack, and then once they attack they are immune to EAR.